Inducing Radicality in Gold-Coordinated Porphyrinoids Through Precise Tip-Induced Covalent Bond Dissociation.

π-Extended porphyrinoids are versatile platforms for the emerging field of π-electron magnetism in conjugated systems. However, achieving controlled bond-selective transformations that enable tuning of their electronic ground states remains a major challenge. Here, we propose a protocol for covalent bond dissociation in π-extended porphyrinoids at carbonitrile-Au substituents. By applying bias pulses with an STM tip positioned close to the molecule, the ligand can be selectively cleaved, resulting in chemisorption of the porphyrinoid onto the Au(111) surface. BR-STM provides structural insights into the bonding configurations before and after the scission, while STS in combination with DFT+CASCI calculations reveals the impact of the cleavage on the molecule's electronic properties. Whereas the intact molecule exhibits a closed-shell electronic structure, removal of the ligands induces a change in its electronic ground state, leading to the emergence of a Kondo resonance upon cleavage of the CN─Au ligands. In addition, DFT + vdW simulations show that carbonitrile─Au coordination weakens the carbon─carbon bond connecting the ligand to the molecular core, thereby facilitating its cleavage through tip-induced manipulation. Overall, these results provide insights into the bonding nature of the carbonitrile─Au interaction and demonstrate how the bond scission induces a transition from closed-shell to open-shell states.